Virtually all eukaryotic organisms appropriately examined have been shown to possess the capacity for endogenous temporal control and organization known as a circadian rhythm. The cellular machinery responsible for generating rhythms is collectively known as the biological clock. A healthy circadian clock underlies both physical and mental health. Because of the ubiquity of its influence on human mental and physiological processes - from circadian changes in basic human physiology to the clear involvement of rhythms in work/rest cycles and sleep - understanding the clock is basic to prevention and treatment of many physical and mental illnesses. Our specific aims are designed to further our understanding of the means through which the clock generates biological time. Post-translational modification, chiefly phosphorylation, of clock proteins is central to their function. Specific Aim #1 is focused on the complete identification of phosphorylation sites in clock proteins, how they change with time, and how this impacts the proteins' activities. Specific Aim #2 focuses on understanding the dynamics of the oscillator, how it achieves temperature compensation, and the molecular details of how the parts interact. Efforts to reconstruct the oscillator will continue. Specific Aim #3 builds upon our strong grounding in genomics and genetics which we will harness to identify novel components required for oscillator function and determine the means through which they act. Our long term goals are to describe, in the language of genetics and biochemistry, the feedback cycle comprising the circadian clock, how this cycle is synchronized with the environment, and how time information generated by the feedback cycle is used to regulate the behavior of cells and organisms. These projects are complementary and mutually enriching in that they rely on genetic and molecular techniques to dissect, and ultimately to understand, the organization of the cell as a function of time. [unreadable] PUBLIC HEALTH RELEVANCE: Virtually all eukaryotic organisms appropriately examined have been shown to possess the capacity for endogenous temporal control and organization known as a circadian rhythm, the output of a biological clock. A healthy circadian clock underlies both physical and mental health. Because of the ubiquity of its influence on human mental and physiological processes - from circadian changes in basic human physiology to the clear involvement of rhythms in work/rest cycles and sleep - understanding the clock is basic to prevention and treatment of many physical and mental illnesses. [unreadable] [unreadable] [unreadable]